It's very rugged. Most touring bikes have some flex in them.
This one doesn't.
.

An overly stiff frame is not an asset on tour unless you are a very heavy rider with a very heavy load. You do need a frame that is stiff enough for your specific case, but I'd caution against buying the stiffest frame possible unless you need it. The ride quality and performance will suffer.

Frame $975, then fork is extra. It seems the Surly LHT trucker frame and fork are similar but with slightly more tour-friendly features -- two sets of fork eyelets on dropout, spoke mounts, and options for 26" wheels -- for less than 1/2 the cost at ~$450 or less. In fact, for price of the Gunnar, one could get a complete Surly LHT. Perhaps made in the USA and difference in frame material justifies the price for some.

P.S. Looking at frame geometry, the LHT also seems to have aspects that more tour-centric. For example, longer wheel base and longer chainstays.

Ideally, I want a nice all rounder for unloaded long rides, but still can do the loaded touring. The owner of my LBS, calling loaded touring bikes "Prairie Schooners", thinks the Gunnar would provide a more "supple" ride unloaded. Also suggested looking into a 'Cross bike, as that would also provide a more spirited ride unloaded, and perform better on gravel roads. I know many on this forum have gone that route. This will be my project next winter. It will be my "Dream Bike" but my funds are not unlimited, if you know what I mean.

Ideally, I want a nice all rounder for unloaded long rides, but still can do the loaded touring. The owner of my LBS, calling loaded touring bikes "Prairie Schooners", thinks the Gunnar would provide a more "supple" ride unloaded.

See if you can get the tubing diameters and wall thicknesses for the bikes in question. That will tell you a lot about how they'll ride.

BTW - my latest bike is a Waterford built steel frame made from the smallest thinest tubing they'd use for my 59cm TT. Rides wonderfully. Too light for a loaded touring rig of course, but I'll be doing some fast credit card tours on it this year.

Frame $975, then fork is extra. It seems the Surly LHT trucker frame and fork are similar but with slightly more tour-friendly features -- two sets of fork eyelets on dropout, spoke mounts, and options for 26" wheels -- for less than 1/2 the cost at ~$450 or less. In fact, for price of the Gunnar, one could get a complete Surly LHT. Perhaps made in the USA and difference in frame material justifies the price for some.

P.S. Looking at frame geometry, the LHT also seems to have aspects that more tour-centric. For example, longer wheel base and longer chainstays.

Ideally, I want a nice all rounder for unloaded long rides, but still can do the loaded touring. The owner of my LBS, calling loaded touring bikes "Prairie Schooners", thinks the Gunnar would provide a more "supple" ride unloaded. Also suggested looking into a 'Cross bike, as that would also provide a more spirited ride unloaded, and perform better on gravel roads. I know many on this forum have gone that route. This will be my project next winter. It will be my "Dream Bike" but my funds are not unlimited, if you know what I mean.

Another option would be Gunnar's Fast Lane. A lot of cross bikes are actually all-rounders. Which is what this is.
It's short for a tourer, but much better for unloaded riding than a touring frame would be.

How much difference is required for you to take notice or find it meaningful? As clarification, Surly claims the chainstay length is 460mm on all LHT frame sizes. Grand Tour varies from 430 to 460, difference of 30 to 0 between the two frame models. Not sure where you identified the 5mm difference.

I would be willing to be bet that the Gunnar is lighter, rides better and has much better build quality than the LHT. Nothing wrong with a LHT, but Gunnars are simply better bikes if you've got the money to pay the difference. Plus you can get a Gunnar painted just about any color and get custom geometry for an upcharge.

Also check out the Soma Saga, which costs about the same as a LHT and has a geometry more favorable to many people (taller head tube, shorter top tube).

BTW, I bought a Bob Jackson World Tour for commuting direct from England, and it didn't cost that much more than a LHT ($630). They will paint your bike in just about any color/decal combination. The BJ World Tour is designed for loaded touring, so it rides stiffer (unloaded) than a typical road bike or sport tourer. In contrast, my Salsa Casseroll (a sport tourer) has much more comfortable ride unloaded with comparable tires.

I would be willing to be bet that the Gunnar is lighter, rides better and has much better build quality than the LHT. Nothing wrong with a LHT, but Gunnars are simply better bikes if you've got the money to pay the difference. Plus you can get a Gunnar painted just about any color and get custom geometry for an upcharge.

I'm not saying you are wrong, but looking at the GT webpage they really don't tell you what the bike is made from or what it weighs. I prefer a curved steel fork for comfort and since there is no disc brake on that bike I don't see the point. In terms of build quality Surly's are pretty good. You don't see them falling apart and if there is a small issue with your bike they simply give you a new frame.

Your last point is the most important if you need something semi-custom to make it work for you.

I've had two Waterford bikes and they were both lovely. My latest one has paint issues - stunning custom colour, but chips off if you look at it funny. I also own 4 Surly bikes and they are some of my favourites.

The reason I would go back to Waterford vs. buying another Surly would be to get a low trail front end geometry and to get light tubing for better frame flex. Surly uses fairly stiff tubing and high trail geometry on bikes like the LHT. OTOH if the bike in question has a stiff frame [which looks likely by the PR spew] and has a standard high trail front end than I'd spend my $$ on a LHT and get a custom paint job if I wanted something unique.

BTW - I've owned several touring bikes that most would agree were "better" than the LHT. After riding them for a year or so I sold them and I still own my LHT.